The invention relates generally to an apparatus for variable image printing. More particularly, the invention relates to an inkjet printer for printing variable identifying information on plain paper label stock, linerless label stock and tape to be applied to the outside of a container, such as a cardboard box or carton.
Manufacturers of products who ship their goods in a container, such as a cardboard box or carton, referred to herein as a case, often desire to apply a label to the outside of the case. The label typically has identifying information, such as product codes, stock or lot numbers, bar codes and shipping data, printed thereon to identify the manufacturer of the goods, the contents of the case or the destination of the case. The label has a first side, referred to herein as the face, on which the identifying information is printed and a second side opposite the face which is coated with a pressure sensitive adhesive. The adhesive side of the label is applied to the outside of the case so that the identifying information on the face of the label is available to be read either manually or by an electronic scanner.
If the identifying information for two or more successive cases is the same, it can be pre-printed on the label, for example, by a flexo-graphic printing process, and applied to the outside of the case by a conventional label applicator. Often, however, the identifying information for successive cases varies so that the manufacturer, the contents, or the destination of a single case or a series of cases can be readily identified. The process of printing variable identifying information on a label or on a series of labels is known as variable image printing. The present practice is to print the variable identifying information on plain paper label stock using a direct contact printer immediately before the label is applied to the case. As used herein, the term plain paper label stock refers to labels having a plain paper surface on one side and an activated chemical adhesive surface on the other side that is protected by a liner coated with a release film which must be removed before the label is applied to the case.
Plain paper label stock, linerless label stock and tape can be manufactured in a continuous roll and wound onto a spool mounted on an unwind spool spindle driven by a conventional motor. Plain paper label stock, however, is expensive relative to linerless label stock and tape. In addition, plain paper label stock requires specially designed equipment to remove the liner before the label is applied to the case. Plain paper label stock is typically applied to the case by a tamp head positioned on the end of a pneumatic or hydraulic tamp. The plain paper label stock is held on the face of the tamp by a vacuum created behind the tamp head and is transferred to the case by activating an air jet in the direction of the case. The liner of the plain paper label stock, however, must be removed before the label is transferred to the case. Further, the equipment required to position the plain paper label stock on the tamp head and to transfer the label to the case is susceptible to misfeeding and malfunctioning. Thus, the cost of variable image printing on plain paper label stock and the additional equipment required to remove the liner and apply the label to a case decreases the productivity and increases the complexity of the labeling process.
The same manufacturers often utilize automated production lines to package, seal and label cases. A typical production line includes a sealing station where the case is sealed with an adhesive sealing tape and a separate labeling station where a plain paper stock label is applied to the case. If variable identifying information is to be printed on the label, the labeling station includes a variable image printer. It has long been recognized that combining the sealing and labeling stations would result in increased productivity, and thus increase profitability. However, the full advantages of a combined sealing and labeling station cannot be realized unless the station is capable of printing variable identifying information onto a label and sealing the case with the label at the same speed or faster than the speed of the production line, which is between about 8 and about 24 inches per second, and preferably is at least about 16 inches per second. Direct contact variable image printers, and in particular thermal transfer printers, are limited to operating speeds of less than about 12 inches per second at a resolution of about 300 dots per inch or less.
As a result, manufacturers presently combine the tasks of sealing and labeling a case only when the information to be printed on the labels is constant. This is accomplished by utilizing a continuous roll of linerless label stock or adhesive sealing tape having the identifying information preprinted on the face of the linerless label stock or tape. Until now, the difficulties that manufacturers have had to overcome to simultaneously seal and label a case when variable identifying information is to be printed on the linerless label stock or tape have proven insurmountable. The primary difficulty is that the adhesive side of the linerless label stock or tape must be supported against the pressure of the print head as the ink is transferred to the face of the label or tape. As a result, the adhesive side of the linerless label stock or tape adheres to the supporting structure, typically one or more platen rollers, or the adhesive accumulates on the exterior surfaces of the supporting structure. Another difficulty is that conventional ink formulations do not adequately adhere to the release agent on the face of the linerless label stock or tape. A further difficulty is that the linerless label stock or tape must be printed and applied at a rate that is compatible with a conventional high-speed production line.
The adhesive side of the linerless label stock or tape can be supported against the pressure of the print head by a platen roller having a TEFLON(copyright), silicon or plasma exterior surface, or that is itself coated with a suitable release film. The linerless label stock and tape currently utilized for sealing cases, however, typically have an exceptionally strong adhesive to insure that the case does not break open during handling. Over time, the adhesive accumulates on the platen roller or strips the TEFLON(copyright), silicon, plasma or release film from the exterior surface of the platen roller. If either instance occurs, the case will likely be inadequately sealed. Thus, the condition of the platen roller and the adhesive on the linerless label stock or tape must be monitored closely. The platen roller must be replaced or the coating must be reapplied at regular intervals, thereby decreasing productivity and increasing the maintenance required to operate the combined sealing and labeling station on the production line.
A dry chemical adhesive that must be wetted to activate the adhesive could be used, and the linerless label stock or tape could be printed with the variable identifying information just before the adhesive is wetted. The platen roller would then support only the dry adhesive side of the linerless label stock or tape against the pressure of the print head while the variable identifying information is printed. A dry adhesive that requires wetting immediately prior to application, however, typically does not produce an adhesive bond that is adequate to insure that the case remains closed during normal handling and shipping conditions. Further, the use of a dry chemical adhesive requires the introduction of an additional mechanism to activate the adhesive. Any such additional mechanism increases the complexity of the sealing and labeling station, thereby decreasing productivity and increasing the maintenance required to operate the combined sealing and labeling station on the production line.
The assignee of the present invention has previously developed a unique thermal transfer printer for variable image printing on a continuous roll of linerless label stock and tape. The thermal transfer printer includes a captive tape guide that supports the adhesive side of the linerless label stock or tape against the pressure of the print head while minimizing the amount of adhesive that accumulates on the platen roller. The thermal transfer printer further utilizes a unique ink formulation that adheres to the release agent on the face of the linerless label stock or tape or to the underlying substrate. The thermal transfer printer, however, is limited in operating speed to about 12 inches per second at a resolution of about 300 dots per inch. Accordingly, the thermal transfer printer cannot print variable identifying information at a rate that is compatible with the operating speed of a conventional high-speed production line. As a result, productivity is sacrificed when the thermal transfer printer is utilized in connection with a combined sealing and labeling station on a conventional high-speed production line.
As is thus apparent, there is an acute need for an apparatus for printing variable identifying information on plain paper label stock, linerless label stock and tape at a speed approaching the operating speed of a conventional high-speed production line. More specifically, there is a need for an apparatus for printing variable identifying information on plain paper label stock, linerless label stock and tape that is to be applied to a case to convey identifying information, such as product codes, stock or lot numbers, bar codes and shipping data, to identify the manufacturer of the goods, the contents of the case or the destination of the case. In particular, a combined sealing and labeling station is needed that is capable of printing variable identifying information on adhesive sealing tape at a speed approaching the operating speed of a conventional high-speed production line. Such a combined sealing and labeling station would make it possible to combine the tasks of sealing and labeling a case on a conventional high-speed production line without decreasing productivity or increasing the complexity or the maintenance of the sealing and labeling station.
Accordingly, it is a principle object of the invention to provide an apparatus for printing variable identifying information on plain paper label stock, linerless label stock and tape at a speed greater than about 12 inches per second at a print resolution of at least about 300 dots per inch. More particularly, it is an object of the invention to provide an apparatus for printing variable identifying information, such as product codes, stock or lot numbers, bar codes and shipping data, on plain paper label stock, linerless label stock and tape that is to be applied to a case to identify the manufacturer of the goods, the contents of the case or the destination of the case.
It is yet another object of the invention to provide a combined sealing and labeling station including an apparatus for sealing and labeling a case on a conventional high-speed production line that is capable of printing variable identifying information on the face of adhesive sealing tape at a speed greater than about 12 inches per second at a print resolution of at least about 300 dots per inch.
It is yet a further object of the invention to provide a combined sealing and labeling station including an apparatus for sealing and labeling a case on a conventional high-speed production line with adhesive sealing tape having variable identifying information printed thereon without decreasing productivity or increasing the complexity and maintenance of the sealing and labeling station.
The invention is an apparatus for printing variable identifying information, such as the contents of a container, the manufacturer of the contents or the destination of the case, on a thin, relatively narrow, continuous roll of plain paper label stock, linerless label stock or tape. The plain paper label stock, linerless label stock or tape has a first side and a second side. Preferably, the first side of the tape has a release agent thereon and the second side has an activated chemical adhesive thereon. The apparatus includes an inkjet printer for printing variable identifying information on the first side of the tape. The inkjet printer includes an unwind spool spindle and an unwind spool for supporting the continuous roll of the plain paper label stock, linerless label stock or tape. The unwind spool is rotatably mounted on the unwind spool spindle so that the continuous roll of plain paper label stock, linerless label stock or tape may be unwound from the spool on demand. The inkjet printer also includes at least one inkjet print head for applying ink to the first side of the plain paper label stock, linerless label stock or tape. The inkjet printer further includes guide and roller means for guiding the plain paper label stock, linerless label stock or tape past the inkjet print head and means for advancing the plain paper label stock, linerless label stock or tape on demand. Preferably, the inkjet printer prints the variable identifying information on the plain paper label stock, linerless label stock or tape at a rate that is compatible with the operating speed of a tape applicator on a conventional high-speed production line.
The guide and roller means for guiding the plain paper label stock, linerless label stock or tape past the inkjet print head includes a pair of opposed guide rollers, a nip roller assembly and a driven platen roller opposite the inkjet print head. The pair of opposed guide rollers includes an upper guide roller and a lower guide roller. The nip roller assembly includes a driven feed roller and a stationary nip roller opposite the driven feed roller. The means for advancing the plain paper label stock, linerless label stock or tape on demand includes a direct current (DC) servo motor mechanically connected to the driven feed roller and the driven platen roller. The servo motor includes a drive shaft that simultaneously drives the driven feed roller and the driven platen roller to advance the plain paper label stock, linerless label stock or tape past the inkjet print head. The lower guide roller, the driven feed roller and the driven platen roller support the adhesive side of the linerless label stock or tape while maintaining consistent alignment of the face of the linerless label stock or tape opposite the inkjet print head. The opposed guide rollers, the driven feed roller and the driven platen roller each have an exterior surface coating thereon that prevents the activated chemical adhesive from accumulating on the rollers.
Preferably, the ink is a unique formulation of resin and wax in which the resin is specially engineered to print on the release agent on the face of the linerless label stock or tape and the wax is specially engineered to adhere the print to the release agent on the face of the tape. Thus, the uniquely formulated ink optimizes the adherence, bleed resistance, visibility, flexibility and utility requirements for printing the variable identifying information on the face of the tape. In one of the preferred embodiments, the inkjet printer further includes a melt tank for melting solid blocks of ink and one or more conventional heating elements positioned within the melt tank. A thermocouple monitors the temperature of the melted ink within the melt tank. The melted ink is delivered to the inkjet print head by an ink pump that is in fluid communication with the melt tank through a heated conduit.
The inkjet printer further includes a fuser for drying the ink immediately after the variable identifying information is printed on the tape. In one preferred embodiment, the fuser includes a blower unit that generates a stream of ambient air. The blower unit is in fluid communication with a pneumatic chamber through an exhaust port. The pneumatic chamber is connected to a nozzle that has a truncated, conical entrance port and a small diameter, cylindrical exit port for directing the stream of air onto the first side of the tape. A butterfly valve is positioned between the pneumatic chamber and the entrance port of the nozzle for varying the amount of air that is permitted to enter and subsequently exit the nozzle. In another preferred embodiment, the fuser may further include a heating coil consisting of one or more conventional heating elements positioned within the pneumatic chamber for heating the ambient air. A thermocouple may also be provided to monitor the temperature of the heated air inside the pneumatic chamber. In another preferred embodiment, an ultraviolet light bulb is positioned within the pneumatic chamber and at least one light shutter is positioned between the pneumatic chamber and the entrance port of the nozzle to vary the amount of ultraviolet light that is permitted to enter and subsequently exit the nozzle. In yet another preferred embodiment, a cooling coil consisting of one or more conventional cooling elements positioned within the pneumatic chamber for cooling the ambient air. A thermocouple may also be provided to monitor the temperature of the cooled air inside the pneumatic chamber.